Lack of sex in a relationship...

I am 24 years old and have a normal to high sex drive, my boyfriend of 2 years is 28 and seems to never want to have sex. It gets to the point where I feel like I have to beg for it. Or when we do its only because he feels like he has to. This has just started over the past couple of months and is becoming a huge problem in our relationship. any ideas on what I can try to get the sexual spark back that we had? Or is anyone else in a situation like mine?